Object.prototype.watch() - Archive of obsolete content | MDNWatches for assignment to a property named prop in this object, calling handler(prop, oldval, newval) whenever prop is set and storing the return value in that property. A watchpoint can filter (or nullify) the value assignment, by returning a modified newval (or by returning oldval). If you delete a property for which a watchpoint has been set, that watchpoint does not disappear. If you later rec
